This invention relates to a method of, and an apparatus for, producing a fiber-reinforced resin golf club shaft. More particularly, this invention relates to a method of, and an apparatus, for producing a fiber-reinforced resin golf club shaft which can carry out continuously and simultaneously and in one process step an operation of winding a tape made of an organic polymer on the full length of a shaft substrate and an operation of winding a tape on only a part of the shaft substrate.
When the shaft weight of golf club shafts in general is reduced for the same shaft length, a moment using a certain point in the proximity of a grip portion as a support point (or a swing balance) becomes small. Therefore, head speed and controllability of a ball's orbit can be improved, flying distance can be increased and directionality can be stabilized. When the shaft weight is decreased for the same swing balance, the club length can be increased and the head weight can be increased, as well. Therefore, an increase in the flying distance can be expected.
However, when the shaft weight is decreased, its strength becomes insufficient. To supplement this insufficiency, partial reinforcement of the shaft must be made. Greater reinforcement is necessary particularly for the tip side (the fitting side of the shaft to the head) which receives the greatest impact force when a ball is hit by the club head. In the case of fiber-reinforced resin golf club shafts, for example, the number of laminate layers of a fiber-reinforced resin sheet is increased on the tip side when the shaft is made.
When the reinforcement structure described above is employed, however, the centroid position of the shaft shifts towards the tip side. Therefore, even when the shaft weight is decreased, the swing balance of the shaft can be hardly reduced. Further, the effect of an increase of the head weight and the effect of an increase of the shaft length cannot be expected, either, at the same swing balance by merely reducing the total weight.
An inventors of the present invention previously filed patent application Ser. No. 08/533,748 (now U.S. Pat. No. 5,634,861) for a shaft having the structure of a fiber-reinforced resin golf club shaft which solves the problems described above. In this golf club shaft, a tape made of an organic polymer is wound only on the distal end portion of the shaft by varying a winding pitch.
When such a fiber-reinforced resin golf club shaft is molded, shape retention of an uncured fiber-reinforced resin, discharge of an excessive resin and volume compression of air are carried out at the time of molding of the shaft. Therefore, a tape wrapping step of winding a heat-shrinkable polymer having good mold releasability on the full length of the shaft is necessary.
According to the prior art method, however, at least two steps, that is, a step of wrapping the tape at the distal end portion and the step of wrapping the tape on the shaft throughout its full length, are necessary, and there remains the problem that the work efficiency and productivity are extremely low.